Hydraulic hose is indispensable in many industrial applications. For example, on various earth moving vehicles, hydraulic hose carries pressurized hydraulic fluid from a pump or pumps to one or more hydraulic cylinders provided on the vehicle to perform useful work. In the case of a loader, the hydraulic cylinders may be mounted so as to raise and lower one or more lifts arms, and then other hydraulic cylinders may be used to tilt or otherwise move a bucket or other implement mounted to the end of the lift arms.
In order to operate effectively, such hoses must communicate hydraulic fluid under very high pressures and under extreme temperature and work environments. Moreover, they must be manufactured to have high duty cycles enabling repeated use under such conditions for an extended period of time. The hose itself is typically manufactured with an inner liner manufactured from an elastomeric material enabling sealed communication of the hydraulic fluid, while enabling the hose to bend, twist, and turn as needed for operation of the vehicle. However, as the hydraulic fluid is under such extreme pressures, the elastomeric liner is then surrounded by a reinforcing layer, typically manufactured from metallic strands wrapped around the liner. Finally, to protect the liner and reinforcing layer from the ambient conditions, temperatures, and repeated abrasions likely to be encountered, the reinforcing layer is then typically surrounded with an elastomeric cover.
In order to connect such hose to the aforementioned cylinders and pumps, various types of couplings have been devised. Traditionally, the couplings would require the end of the hose to be skived wherein the outer cover of elastomeric material is shaved away down to the metallic reinforcing layer. Only when skived would the coupling be mounted directly to the underlying metal. As such couplings are, by necessity, relatively labor intensive and rely on the skill of the laborer to effect a good coupling and seal, no-skive couplings were introduced and have now been commonplace for some time. With a no-skive coupling, the hose is not altered at all, but rather the coupling is designed to penetrate the outer cover and engage the underlying metal to affect the seal.
Such no-skive couplings typically are attached to the end of the hose by crimping, swaging or some other form of mechanical force. More specifically, the coupling is slid onto the end of the hose in relatively loose fashion, and then a radially inwardly directed force is applied. In order to facilitate this process, a no-skive coupling includes an inner stem which is inserted into the hose, and an outer shell or ferrule extending from the stem and surrounding the outer cover of the hose. The shell is spaced from the stem so as to define an annular space adapted to receive the hose. Barbs or other surface features extend from the shell and/or stem to penetrate the hose during the crimping process to form a tight connection.
While effective, the attachment of the ferrule to the stem has proven to be, and continues to be, problematic. Currently, the ferrule and stem are separately manufactured and then mechanically joined together in a cold-forming process. In the cold-forming process, also known as staking, the ferrule is positioned around the stem and then a staking punch mechanically compresses the ferrule toward, and into, the stem. Sometimes the resulting interference fit is sufficient, but often times the interference fit loosens after repeated use and the ferrule begins to rotate about the stem. This is problematic for a number of reasons. One, such hydraulic hoses carry highly pressurized hydraulic fluid that must be communicated to the hydraulic cylinders in sealed fashion. Any rotating of the ferrule relative to the stem threatens the efficacy of that seal. Secondly, the coupling typically needs to be attached to the cylinder, pump, or the like, in a particular rotational orientation. If the rotational position of the ferrule relative to the stem changes, or is not reliably oriented, the connection cannot be made as easily or sometimes at all.